EP1238877B1 - Vehicle brake device provided with electronics for determining a vehicle referencespeed - Google Patents

Description

The present invention relates to a vehicle brake system according to the preamble of claim 1, see e.g. document DE-A-19 930 561. Document DE-A-3 441 103 states that two wheel speed sensors are attached can be used to detect a defective pulse from an asynchronous machine.

Modern road and rail vehicles are usually included an anti-lock device fitted to road vehicles as an "ABS system" and as a rail vehicle "Anti-skid system" is called. ABS systems and anti-skid systems the brake pressures on individual wheels or Adjust the axles of the vehicle so that the wheels lock or wheel sets prevented and the braking distance is minimized. For such a brake pressure control is required at the ' individual wheels or axles existing slip values, which from the respective wheel speeds and the actual Vehicle speed can be determined. This is usually done Wheel speed sensors are provided, being from the individual Wheel speeds are an approximation of the actual vehicle speed is calculated, which is referred to below as the "reference speed" referred to as.

Especially with poor adhesion values between the bike and the road the reference speed significantly influences the braking force control on the wheels. An "incorrect" reference speed can lead to errors in the braking force control of the whole Vehicle. For good ABS or anti-skid control is therefore an exact determination of the actual Vehicle speed, i.e. the reference speed required. Especially for vehicles that only have a single independent braking force control system reduced adhesion between wheel and rail, should therefore high security against individual errors can be ensured.

From DE 39 31 313 A1 an anti-lock braking system for a Motorbike known, in which the front wheel and the rear wheel a speed sensor is assigned. To determine the Wheel slips are used here for the front wheel and the rear wheel each approximate the actual vehicle speed Reference speed determined.

ABS or anti-skid systems are usually single-channel built up, i.e. the wheel speed is per wheel or per wheel group detected by a single wheel speed sensor. If a pulse generator, i.e. a wheel speed sensor fails, that is or are the assigned wheels "unprotected", i.e. they can no longer be regulated according to the wheel speed.

If from a defective wheel speed sensor a "wrong" Wheel speed is delivered and in the reference speed incoming, there is a risk that on all axes the brake pressure is erroneously reduced or that at all Axes the traction is faulty or limited.

This means that incorrect wheel speed signals set the reference speed value as far as possible not falsify, show from applicant's internal State of the art algorithms for calculating the Reference speed a "detection" incorrect Signals on. A reliable detection of all possible errors is however very expensive. In addition, mistakes can already occur during the "error reporting period" so on the calculation of the Reference speed affect that braking force control is adversely affected.

The object of the invention is to provide a brake system which regarding the determination of the actual vehicle speed is optimized and even if a sensor fails no bike leaves unprotected.

This object is achieved by the features of claim 1 solved. Advantageous refinements and developments of Invention can be found in the subclaims.

The basic principle of the invention consists in a brake system a brake electronics and connected wheel speed sensors in that each wheel to be monitored or each monitoring wheel group assigned at least two wheel sensors are. During operation, all existing in the vehicle Wheel sensors constantly monitored. The actual Vehicle speed becomes approximate reference speed however at any time only on one of them "Oriented" wheel speed signals recorded wheel sensors. Which of the existing wheel speed sensors for the reference speed is currently to be regarded as authoritative, according to the invention depending on the current driving condition and determined at least one predetermined speed criterion. The invention thus creates an ABS or anti-skid system with fault tolerance against failure of a speed sensor.

Put simply, it is checked whether the vehicle is straight is braked or accelerated or rolls without power. In Depending on the current driving condition, one of the "higher" measured or the "lower" measured wheel speeds the basis of the reference speed determination laid, which is explained in more detail.

According to a development of the invention, the reference speed with the vehicle braked at the second highest wheel speed oriented. Alternatively, it can also be provided be that when the vehicle is braked, first of all "speed pairs" the minimum speed of the wheel speed sensors assigned to each other is determined. The reference speed will be then at the current maximum of these minimum speeds oriented.

When the vehicle is not braked, especially when the vehicle is driven Vehicle (traction) can change the reference speed at the second lowest wheel speed. alternative it can be provided that when the vehicle is not braked first the maximum speed from each speed pair is determined and that the reference speed is then on Minimum of these maximum speeds is oriented.

When braking, it is thus ensured that a fault due to high speed signal the reference speed is not affected. Accordingly, when the vehicle is not braked or in the "traction" state, it is too low due to the fault Wheel speed signal "hidden".

The detection of the wheel speed signals can either by a only control unit or alternatively to several Control units can be divided if e.g. the number of available Inputs from a control unit are not sufficient. At a The wheel speed signals are divided into several control units between the control units exchanged via a data bus.

a) der ABS- bzw. Gleitschutzregelung wird die höhere der von den einander zugeordneten Radsensoren gelieferten Radgeschwindigkeiten zugrunde gelegt, und zwar dann, wenn in einem Fahrzustand die "Absicherung gegen irrtümliches Lösen der Bremse" höchste Priorität hat, z.B. bei alleinfahrendem Fahrzeug; oder

b) der ABS- bzw. Gleitschutzregelung wird die niedrigere der beiden Radgeschwindigkeiten zugrunde gelegt, wenn "der Blockierschutz" höchste Priorität hat, z.B. bei einem Zug, der aus mehreren Wagen besteht.

Since two wheel speed sensors are assigned to a wheel or a wheel group according to the invention, it must also be determined which of the two wheel speed sensors is decisive for the braking force control, ie the ABS or anti-skid control and the ASR control on the respective wheel or the respective wheel group should be. If you first consider the ABS or anti-skid regulation, the following can be provided:

a) the ABS or anti-skid control is based on the higher of the wheel speeds supplied by the wheel sensors assigned to one another, specifically when "protection against erroneous brake release" has top priority in a driving state, for example when the vehicle is traveling alone; or

b) the ABS or anti-skid control is based on the lower of the two wheel speeds if "anti-lock protection" has the highest priority, eg for a train consisting of several cars.

a) der ASR-Regelung wird die niedrigere der beiden Radgeschwindigkeiten zugrunde gelegt, wenn die "Absicherung gegen einen irrtümlichen Abbau der Traktionskraft" höchste Priorität hat; oder

b) der ASR-Regelung wird die höhere der beiden Radgeschwindigkeiten zugrunde gelegt, wenn das Durchdrehen eines Rades mit höchster Priorität verhindert werden soll.

With regard to the driving force control (ASR or anti-skid control) of a wheel, the following can be provided:

a) The ASR regulation is based on the lower of the two wheel speeds if "protection against erroneous reduction in traction power" has the highest priority; or

b) The ASR control is based on the higher of the two wheel speeds if the spinning of a wheel with the highest priority is to be prevented.

According to a development of the invention it is provided that all wheel speed signals through monitoring electronics be subjected to a plausibility check. If for a Wheel speed signal an error is detected or if a wheel speed signal is considered implausible, which e.g. through a Sensor failure or due to sensor signal peaks due to external electromagnetic interference fields can be caused, then after a corresponding "error disclosure time" (time until Error is detected) this wheel speed signal no longer in the Determination of the reference speed and also no longer in the regulation of the braking or driving force of the assigned Rades or the wheel group included. In such a case then only the second "channel", i.e. the assigned other wheel speed sensor evaluated.

The invention is therefore based on the approach that the electronics, but the "periphery", i.e. especially the sensors is the main source of error. Because sensors fall considerably more often than the brake electronics themselves Difference to the above DE 39 31 313 A1 leaves the invention the "idea of the 2-channel nature of the reference speed", according to which a "separate" for each wheel or wheel group Reference speed is determined.

Rather, according to the invention, a "double", i.e. Really redundant wheel speed detection provided. A single mistake a sensor does not affect the entire brake control of the vehicle, because besides the faulty one intact speed information of the "affected" wheel or the wheel group concerned is present.

A key point of the invention is that described above "Selection Logic". The selection logic enables fast and easy decision which of two are assigned to each other Sensors from a security or availability point of view provides the "more accurate or more realistic" signal. So can very fast, i.e. during an error detection time that sensor of a sensor pair are "discarded", the inclusion of which has an adverse effect on the regulatory objective, for example, its inclusion in the reference speed formation adversely affect driving safety would. A single sensor can determine the reference speed So do not influence so that all or part of the Vehicle brakes are erroneously "braked".

In particular, the individual brake pressure control is from an individual error of a sensor affected wheel as a rule unlimited possible. If the faulty sensor detects after the error detection time has elapsed automatically accessed the intact sensor which of the Logic for this bike is always available here, so that no loss of controllability accepted Need to become. Before the error detection time expires or at Errors where it cannot be decided which of the two different sensors is disturbed, will be accordingly of the criteria explained above is either a decision in favor of driving safety or in favor of availability met. When deciding in favor of driving safety the sensor is considered "valid", the lower one Wheel slip, i.e. which indicates less braking. At a The sensor is considered a decision in favor of availability viewed as "valid" indicating the greater wheel slip, i.e. which indicates greater braking of the wheel or the group of wheels.

Compared to conventional braking systems, where only one Wheel speed sensor for determining the wheel speeds is provided, the reference speed determination is based according to the invention on a larger number of sensor signals, what the error safety or the detectability of errors improved.

1. Ein Einzelfehler bei der Radgeschwindigkeitserfassung beeinflußt die Referenzgeschwindigkeitsbildung niemals so, daß die Bremskraft bzw. ein Teil der Bremskraft des Fahrzeuges bzw. die Antriebskraft des Fahrzeuges vollständig abgebaut wird. Dies gilt auch dann, wenn nur ein Steuergerät verwendet wird.

2. Die Möglichkeiten zur Erkennung unplausibler Raddrehzahlsignale sind wesentlich verbessert, da die Anzahl der erfaßten Raddrehzahlen groß ist und die Geschwindigkeiten zentral miteinander verglichen werden können.

3. Durch die redundante Raddrehzahlerfassung können immer zwei Drehzahlsignale eines Rades in die Regelung einbezogen werden. Das Rad bleibt also auch dann geschützt, wenn eines der beiden Drehzahlsignale ausfällt.

4. Die "2-Kanaligkeit" ist durch Verwendung nur eines Steuerrechners kostengünstig realisierbar. Gegenüber einem einkanaligen System sind lediglich Doppelimpulsgeber bzw. zwei einzelne Raddrehzahlgeber erforderlich. Die Verwendung von zwei Steuergeräten ist nicht zwingend erforderlich.

The advantages of the invention can be summarized as follows:

1. A single error in the wheel speed detection never influences the reference speed formation so that the braking force or part of the braking force of the vehicle or the driving force of the vehicle is completely reduced. This also applies if only one control unit is used.

2. The possibilities for recognizing implausible wheel speed signals are significantly improved since the number of detected wheel speeds is large and the speeds can be compared centrally with one another.

3. Thanks to the redundant wheel speed detection, two speed signals from one wheel can always be included in the control. The wheel remains protected even if one of the two speed signals fails.

4. The "2-channel system" can be implemented inexpensively by using only one control computer. Compared to a single-channel system, only double pulse transmitters or two single wheel speed transmitters are required. The use of two control units is not absolutely necessary.

Fig. 1

das Prinzip der Erfindung in schematischer Darstellung;

Fig. 2

den Aufbau der Bremselektronik in vereinfachter Darstellung;

Fig. 3

ein Ausführungsbeispiel eines 4-achsigen Fahrzeuges mit drehzahlmäßig unabhängigen Achsen; und

Fig. 4

ein weiteres Ausführungsbeispiel eines 4-achsigen Fahrzeuges mit drehzahlmäßig unabhängigen Achsen.

The invention is explained in more detail below using an exemplary embodiment in conjunction with the drawing. Show it:

Fig. 1

the principle of the invention in a schematic representation;

Fig. 2

the structure of the brake electronics in a simplified representation;

Fig. 3

an embodiment of a 4-axle vehicle with axles independent of speed; and

Fig. 4

a further embodiment of a 4-axle vehicle with axles independent of speed.

1 shows a rail vehicle 1 with a first bogie 2 and a second bogie 3. The first bogie 2 are the two wheel axles 4, 5 and the second bogie 3 assigned to both wheel axles 6, 7. The wheel axis 4 is kinematic coupled to the wheel axle 5, which is shown here only by a schematic shown push rod is indicated. The wheel axles 4, So 5 have the same actual wheel speed. The same applies to the wheel axles 6, 7. The wheel axles 4, 5 and Wheel axles 6, 7 thus each form a "wheel group" with the same actual wheel speed.

The wheel speeds of the wheel axles 4-7 are assigned by Wheel speed sensors 8-11 sensed. The one from the Wheel speed sensors 8-11 are delivered wheel speed signals evaluated by a control unit 12 which brakes the Controlled bogies 2 and 3 accordingly.

If the brake system is correct, the wheel speed sensors should be 8, 9 and 10, 11 each deliver identical signals. by virtue of of sensor malfunctions or external interference, e.g. electromagnetic interference fields, the sensor pairs 8, 9 or 10, 11, however, differ from each other. Depending on current driving condition, i.e. whether the vehicle is braked or is unbraked, can be based on a speed criterion in each case one sensor from the sensor groups to be regarded as valid 8, 9 or 10, 11 can be selected.

When the vehicle is braked, for example, the reference speed oriented to that of the wheel speed sensors 8-11 which is the second highest wheel speed displays. Alternatively, either of the two provided here can be used Sensor pairs 8, 9 and 10, 11 the sensor with the Minimum speed can be selected. From the two Minimum speed sensors can then determine the maximum speed selected to determine the reference speed (min-max selection).

When the vehicle is not braked, the reference speed can based on the second lowest of the wheel speed sensors 8-11 measured wheel speed can be determined. alternative this can be done by first selecting a maximum of the two speed pairs to be hit. Finally, from the two Maximum speeds the smaller for determining the Reference speed can be used (max-min selection).

The brake pressure control on the wheel axles 4-7 can be done accordingly the security or availability criteria explained above respectively.

2 shows in simplified form the algorithms implemented in a control device according to the invention. The measured wheel speed signals vi are supplied to three blocks, namely a plausibility check 13, an algorithm 14 for calculating the reference speed v _ref and a control algorithm 15 for controlling the drive / braking force z _{i of} an individual wheel or a group of wheels.

The plausibility algorithm 13 makes a "rough selection".

Here it is checked whether individual wheel speed signals v _i are not realistic at all and have to be separated out.

A reference speed v _{ref is} formed from the wheel speed signals v _{i in} accordance with the driving condition and speed criteria explained above. The reference speed calculation v _ref is always "oriented" to a single wheel speed signal. "Orientation" means that the reference speed is not necessarily set equal to the currently decisive wheel speed signal, but that the wheel speed signal is filtered or smoothed if necessary in order to obtain a "smooth" or as realistic a speed curve as possible, which is as good as possible actual vehicle speed is approximated.

The control algorithm 15 determines the wheel slip occurring on the individual wheels or wheel groups, taking into account the wheel speed signals v _i and the reference speed, and controls the drive or braking forces as a function thereof.

Fig. 3 shows a schematic embodiment of the anti-skid or anti-skid system of a 4-axle vehicle, in which, in contrast to FIG. 1, the axes 4-7 in terms of speed are not linked. The speed detection is here divided into two "assemblies", namely the control unit 12 and an expansion module 16, which is connected via a data bus 17 communicate with each other. That is, part of the Wheel speed signals are immediately sent to the control unit 12 and other part of the wheel speed signals of the expansion module 16 fed. The wheel speed signals are from the expansion module 16 sent to the control unit 12. The ones explained above Control algorithms are, however, implemented in control unit 12.

Fig. 4 also shows an embodiment of an anti-skid or anti-skid system for a 4-axle vehicle with independent axles. In contrast to FIG. 3, however, each of the two bogies 2 and 3 is assigned its own control unit 12, 12 'for braking force control. In the control device 12, wheel speed signals v ₁ , v _{1 '} , v ₂ , v _{2 ' are} supplied, and in the control device 12 ', wheel speed signals v ₃ , v _3' , v ₄ , v _{4 '} . The control units 12, 12 'use this to calculate brake control signals 18-21 for the axes 4-7.

Claims (14)

1. Vehicle braking system with wheel sensors connected to an electronic unit for the determination of a reference speed approximating the actual vehicle speed, characterised in that
   at least two wheel.sensors (8, 9; 10, 11) are provided for each wheel or wheel set speed (v_i) to be measured, and
   in that, while evaluating all existing wheel sensors (8-11), the reference speed (v_ref) is at any one instance oriented to one of the existing wheel sensors (8-11), the wheel sensor (8-11) currently ruling the determination of the reference speed being selected in dependence on the current driving state and on at least one preset speed criterion.
2. Vehicle braking system according to claim 1, characterised in that
   exactly two wheel sensors (8, 9; 10,11) are provided for each wheel or wheel set speed (v_i) to be measured.
3. Vehicle braking system according to claim 1 or 2, characterised in that
   the reference speed (v_ref) is oriented to the wheel sensor (8-11) indicating the second highest wheel speed when the vehicle is braked
4. Vehicle braking system according to any of claims 1 to 3, characterised in that the reference speed (v_ref) is oriented to the wheel sensor (8-11) indicating the second lowest wheel speed when the vehicle is not braked.
5. Vehicle braking system according to claim 1 or 2, characterised in that
   one wheel sensor (8, 9; 10, 11) each is selected from the corresponding wheel sensors (8, 9; 10, 11) in dependence on the current driving state with reference to a first speed criterion, and in that the wheel sensor (8, 9; 10, 11 ) currently ruling the determination of the reference speed is determined from the selected wheel sensors (8, 9; 10, 11) with reference to a second speed criterion.
6. Vehicle braking system according to claim 5, characterised in that
   the first and the second speed criteria are extreme value criteria.
7. Vehicle braking system according to claim 5 or 6, characterised in that
   the wheel sensor (8, 9; 10, 11) with the minimum wheel speed is selected from the at least two wheel sensors (8, 9; 10, 11) when the vehicle is braked, and in that the reference speed (v_ref) is oriented to the maximum speed of the selected minimum wheel speeds.
8. Vehicle braking system according to any of claims 5 to 7, characterised in that the wheel sensor (8, 9; 10, 11) with the maximum wheel speed is selected from the at least two wheel sensors (8, 9; 10, 11) when the vehicle is not braked, and in that the reference speed (v_ref) is oriented to the minimum speed of the selected maximum wheel speeds.
9. Vehicle braking system according to any of claims 1 to 8, characterised in that the electronic unit is an ABS/ASR controller (12, 12').
10. Vehicle braking system according to any of claims 1 to 9, characterised in that any ABS operation of the brake pressure control of a wheel or wheel set is based on the higher of the speeds supplied by the at least two corresponding wheel sensors when protection against erroneous reduction of braking force has highest priority.
11. Vehicle braking system according to any of claims 1 to 9, characterised in that any ABS operation of the brake pressure control of a wheel or wheel set is based on the lower of the speeds supplied by the at least two corresponding wheel sensors when anti-lock protection of the wheel or wheel set has highest priority.
12. Vehicle braking system according to any of claims 1 to 11, characterised in that any ABS operation of the brake pressure control of a wheel or wheel set is based on the lower of the speeds supplied by the at least two corresponding wheel sensors when protection against erroneous reduction of traction force at the wheel or wheel set has highest priority.
13. Vehicle braking system according to any of claims 1 to 11, characterised in that any ABS operation of the brake pressure control of a wheel or wheel set is based on the higher of the speeds supplied by the at least two corresponding wheel sensors when protection against spinning of the wheel or wheel set has highest priority.
14. Vehicle braking system according to any of claims 1 to 13, characterised in that a plausibility checking device (13) is provided to subject the signals (v_i) supplied by the wheel speed sensors (8-11) to a plausibility check and to ignore sensors supplying apparently incorrect signals (v_i) when determining reference speed (v_ref) and brake pressure control.

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